Protection of mineral surfaces against spalling



United States Patent This invention relates to the protection of the surface of coal to reduce and prevent rub-off and spalling by coating the srf I. liimaml aaaa mmsitasruulsiqaifi w mfifi aigaatai ama w tix .a a ias. on e. st;- Tliiii'ial pki 99, of c 1 ction from spallifig o'f other exposed mineral surfaces.

This application is a continuation-in-part of application Serial No. 719,999, filed March 10, 1958, and now abandoned.

Coal is formed by the partial decomposition of vegetable matter without free access of air, and sometimes under the effect of increased pressure and temperature. The term coal as used in this specification includes peat, lignite or brown coal, soft or bituminous coal, and hard coal or anthracite, chars and charcoals. The gradation from peat to anthracite is gradual, as the degree of compression and the relative carbon content increases, so that many gradations exist. For example, it is difficult to draw an exact line that distinguishes lignite from bi tuminous coal. All such products are included in the term coal as used herein. Naturally occurring coal may be treated with heat to decrease the volatile content and still be treated in accordance with this invention. Likewise charcoals formed by the incomplete combustion of woods are also included, as these are in effect a product of rapid artificial carbonization, as contrasted with slow natural carbonization, and are generally more porous in nature than the results of natural processes.

Coal in general, and the softer coals, and lignites and peats particularly, are subject to spalling. Spalling is the chipping off of small fragments by the action of weather or abrasion. Spalling also is due to the liberation of contained moisture, which causes the surface of the coal to disintegrate and crumble. In bringing coal from its source in the ground to the final consumer, considerable handling is normally required, and this handling, and associated weathering as the coal is exposed to the elements and also drying and storage, results in the larger pieces of coal being broken up. Many users, particularly domestic consumers, prefer larger pieces of coal. The larger pieces, for example, nut, egg, lump, broken stove, chestnut, pea, etc. sell at a premium as compared with slack, or coal fines.

In using coal there are many occasions where it is desirable that a minimum of the coal rub-0E on the user. It is a desirable, though not a readily achieved goal, to be able to handle coal without soiling the hands or clothing.

In coal mines, similar spalling occurs, and it is desirable to protect the surfaces of exposed coal, as in mine tunnels, and the underground workings, or in surface, or open pit mining from spalling. Loose coal that falls from exposed surfaces increases the explosion hazard underground, and can obstruct passageways. Sandstone, slate, shale, clays in varying states of consolidation, and related mineral formations are solid when first exposed, but on standing also spall, and lose strength. Many such surfaces are wet when first exposed. To be effective, the formation coating material must be applicable to wet surfaces.

It has now been found that the coal surfaces and formation surfaces may be protected by coating the surface by spraying or dipping with an aqueous alkyd resin emul-" [W60 LI Liianui.

3,069,293 Patented Dec. 18, 1962 sion, and then drying the surface to solidify the resin. A thin coat protects from spalling, and to some extent from rub-off. A thicker coating gives better protection. A thin" coating is usually adequate and preferred for economic reasons. Such coatings are particularly useful on the softer coals, or lignites and peats, as these fall apart from weathering or on liberation of contained moisture and at, times unless protected cannot be stored without such attrition as to render the use of the coal uneconomic or highly bothersome due to the excessive disintegration at the surfaces.

Formation surfaces, such as exposed coal veins, in surface mining or underground passages, as well as slate, clays in varying states of consolidation, sandstone and shale surfaces are protected. Underground work is much cleaner, and explosion hazards are reduced, as Well as clean-up efforts to keep loose material from falling on the floor, to present problems of mud, or obstructing water flow, as well as the hazard from falling particles. Pigments such as titanium dioxide or colored dyes may be introduced to show which surfaces have been coated, and aid in maintaining a uniform unbroken coating.

Emulsified alkyd resins in general are satisfactory; commercially available alkyd emulsions may be used. It is desirable that the emulsion be suificiently stable that it may be prepared for use, shipped to the point of use, and applied, without breaking, and that the alkyd resin formed as the water evaporates dry sufiiciently to form' a protective coating which is not unduly soft. The alkyd emulsion may have a drier therein to cause the alkyd resin to harden more rapidly. Suitable driers are cobalt salts of fatty acids such as cobalt tallates. Cobalt naphthenates also are satisfactory driers. Alkyd emulsions may be prepared at the site of application, if desired, and applied directly. The freeze-thaw properties of alkyd emulsions are excellent and this eliminates a difficult storage problem often encountered in applying emulsions. Alkyd emulsions frozen solid at minus C. temperatures have given, on remelting and dilution in water, surface protection equal to that eflfected by the original emulsion before freezing took place.

Alkyd resins as emulsions are particularly effective in forming protective coatings when applied to wet coal. It may be advantageous to pre-wet the surface to -be treated to aid in even distribution. Water alone may be used for wetting the surface. Water containing compounds which enhance wetting is also highly useful particularly when the coal is difficultly wettable. Sodium dioctylsulfosuccinate and related compounds and a variety of other wetting agents may be used. The surface active agents may be incorporated into the emulsion and may be used to aid emulsification of the alkyd resin, thus being present in the emulsion as applied to aid in wetting of the coal surface and to enhance the action of the emulsion in spreading evenly to uniformly protect the surface of the coal.

Emulsions of alkyd resins of 30-50% solids are pre-' pared conveniently and as such may be pumped and sprayed readily on coal. Such emulsions may be diluted to 5 to 30% for convenience in application. The spraying of alkyd emulsions of about 12% concentrations has given excellent results on coal surfaces. The method of application is simple. Portable, hand-operable, spraying equipment such as used for fighting fires is effective for treating limited surface areas. Mechanized spraying equipment such as is employed in applying insecticidal sprays is useful for large scale treatments. The pieces of coal may be dipped in the emulsion. To avoid excess alkyd resin consumption, more dilute emulsions are preferable for dipping.

Alkyd resins are generally made from unsaturated fatty acids, polybasic acids, and polyhydric alcohols. Any of the alkyd resins which are emulsifiable in water may be used in this invention.

The resins described in the copending United States applications, Serial Nos. 575,363, filed April 2, 1956, now United States Patent No. 2,889,293, June 2, 1959, entitled Mixture of Certain Oil-Modified Alkyd Resins Blended With a Resinous Reaction Product of Certain Acids With an Adduct of an Alkylene Oxide With Certain Polyhydric Alcohols," W. L. Hensley, A. I. Kirsch, and R. E. Layman, Jr.; and Serial No. 579,158, filed April 19, 1956, now United States Patent No. 2,889,294, June 2, 1959, entitled Resinous Reaction Product of an Aliphatic Polycarboxylic Acid, Certain Oil Acids, an Adduct of Ethylene Oxide and Certain Polyhydric Alcohols and Rosin Acids, R. E. Layman, Jr., are particularly effective because the emulsions of the resins described in these applications are stable for a long length of time and easily applied to the pieces of coal, or formation surfaces. These particularly effective alkyd resin emulsions are the oil-in-water emulsions of a glyceride oil modified alkyd resin and the alkyd resin prepared from the adduct of a 2 to 4 carbon alkylene oxide with a polyhydric alcohol having at least 5 carbon atoms and at least 4 hydroxy groups, a dibasic aliphatic acid, and an aliphatic unsaturated monobasic acid. These emulsions are particularly conveniently formed under alkaline conditions.

The polycarboxylic acids used are predominately those free from non-benzoic unsaturation and include phthalic, oxalic, malonic, succinic, glutaric, sebacic, adipic, pimelic, suberic, azelaic, citric, tartaric, malic, and tricarballylic acids. These acids, their anhydrides, and mixtures thereof, are conveniently used in the preparation of the alkyd resin. Minor amounts of unsaturated acids may be present including such acids as maleic, fumaric, aconitic, and itaconic. Whereas glycerol is traditionally the polyhydric alchol used in the alkyd resins, other polyhydric alcohols may be used. Such polyhydric alcohols include glycerol, ethylene glycol, diethylene glycol, pinacol, arabitol, xylitol, mannitol, trimethylol propane, trimethylol ethane, sorbitol, pentaerythritol, dipentaerythritol, propylene glycol, dipropylene glycol, other alkane diols and mixtures thereof. Preferably enou h polyhydric alcohol is used to provide an excess of 25% or more over that theoretically required to provide complete esterification.

The oils used to modify the alkyd resins of the emulsion are glyceride oils of either vegetable or animal origin which may be non-drying, semi-drying, or drying and in such proportions as to produce short, medium, or long oil alkyd resins. Among these oils are coconut oil, palm kernel oil, babassu oil, rape seed oil, mustard seed oil. olive oil, sesame oil, corn oil, cottonseed oil, soya oil, sunflower oil, walnut oil, linseed oil, perilla oil, castor oil, either raw or dehydrated, tung oil. oiticica, whale oil, menhaden oil, sardine oil, herring oil and the glycerol esters of fatty acids derived from tall oil fatty acids. These glyceride oils, or the fatty acids derived therefrom, or the mono-glycerides of these fatty acids or combinations thereof are effective.

In preparing the oil-modified alkyd resin of the present invention the esterification of the polycarboxylic acid and the polyhydric alcohol in the presence of the oil is accomplished by heating in a conventional manner to between about 200260 C. for a sufiicient period of time to give an acid number between about 100 and about 5, preferably between about 15 and 20. The adduct which is used with a second quantity of alkyd resin in the preferred embodiment is prepared by reacting alkylene oxides with a polyhydric alcohol having at least 5 carbon atoms and 4 hydroxy groups. Ethylene oxide, propylene oxide, and butylene oxide are particularly effective. The effective polyhydric alcohols include such alcohols as pentaerythritol and dipentaerythritol, sorbitol and mannitol and mixtures thereof. The adducts are prepared by reacting the alkylene oxides and the polyhydric alcohols in the ratio of between about 3 mols and 7 mols of the alkylene oxide per hydroxy group of the polyhydric alcohol. This alcohol-alkylene oxide adduct is reacted with an aliphatic carboxylic acid and a glyceride oil fatty acid, and preferably an unsaturated fatty acid such as those mentioned above. Of the polycarboxylic acids, either the saturated or the unsaturated can readily be utilized. The alpha, beta ethylenically unsaturated polycarboxylic acids which may be used include maleic, fumaric, aconitic, and itaconic and their anhydrides. These acids and/or their anhydrides may be singly used, or in combination. Amongst the saturated aliphatic polycarboxylic acids which may be used are malonic, succinic, glutaric, sebacic, adipic, pimelic, suberic, azelaic, citric, tartaric, malic and tricarballylic. These polycarboxylic acids and/or their anhydrides, may be used in combination with one another or in combination with the alpha, beta ethylenically unsaturated polycarboxylic acids and/ or their anhydrides.

Among the fatty acids which are reacted with the adduct together with the aliphatic polycarboxylic acids are the fatty acids derived from animal and vegetable oils. Although these fatty acids may be saturated, for best results, it is preferred that the unsaturated fatty acids be used, particularly those which have 18 carbon atoms in the chain. Illustrative of these preferred fatty acids are oleic, linoleic, linolenic, elaeostearic, licanic, ricinoleic and the like.

For the preparation of the preferred alkyd resin for emulsifying, the conventional oil-modified alkyd resin is prepared and then the second component containing the alkylene oxide condensate with the polyhydric alcohol is poured with stirring into the first alkyd resin, both components being warm. When the blending has been completed, the mixture is poured into water and dispersed therein.

Alkaline dispersing agents such as the nitrogenous bases are particularly effective in forming the stable emulsion. The amount of the alkyd resin mixture can vary so that the final composition has from 5 to 60% solids therein. A solids content of from 40 to 50% is particularly effective.

The resin emulsion may be conveniently applied by spraying the surface of the coal or by dipping. A preferred rate of application is from 1 to 50 pounds of resins solids per ton of coal. The smaller amounts are used with the more solid, firm, hard coals in larger lumps. For spraying a dilution of 2 to 25% of resin solids is preferred. For dipping more dilute solutions of 1 to 15% of resin solids are very useful.

For coal surfaces, or slate, sandstone, compacted clays, or shale surfaces, where the original formation is to be maintained intact, an application rate of about 0.25 to about 10 pounds of resin solids per square feet of exposed surface gives good results. For best protection of the surface at least 0.50 pound of resin solids per 100 square feet is required. An application rate of over 5 pounds of resin solids per 100 square feet of exposed surface is frequently not economically justified, although high rates give excellent surface protection. Spraying is the normal method of application to formation surfaces. The emulsion can be applied by a brush, or by a roller, in the unusual situation where the surface is smooth.

A dilution of 2 to 25 resin solids in water is preferred. Concentration of 50% solids can be used, with spray equipment designed for such high solid content emulsions. Such spray equipment is available at low cost. For example, a standard high pressure grouting pump, such as used in applying cement grout is suitable, and frequently already available in mines.

As illustrative of my invention, the following examples disclose certain embodiments.

PREPARATION OF EMULSIONS The following examples in which parts and percentages are by weight describe the preparation and use of certain alkyd emulsions which are within the scope of the invention.

Example 1 In separate flasks there is blended the following two formulations. Each is heated over a period of about two hours at 240-250 C. and each is held at that temperature until the formulation has an acid number of 16 to 20, then cooled to 150 C.

FORMULATION A 148 phthalic anhydride 220 distilled tall oil 28 ethylene glycol 82 pentaerythritol FORMULATION B 5 fumaric acid 33 linseed oil fatty acids 14 gum rosin 63 condensate of 1 mol sorbitol with 30 mols ethylene oxide Formulation B is added to Formulation A and mixed for 30 minutes; the composite is then cooled to 130 C. and over a one hour period is uniformly added to a 2% aqueous solution of morpholine at 95 C. with rapid agitation, so as to obtain a ratio of 55% water phase to 45% resinous phase. After all the resin is added, the emulsion is cooled to room temperature, and is ready for use.

Example 2 One part of the finished emulsion from Example 1 and 1 part emulsified petroleum hydrocarbon resin (50% solids), the resin being characterized by a softening point (ring and ball) of 100 C.-.L3; specific gravity at 25 C. 0.970-.975; refractive index 1.5116; acid number 1; iodine value (Wijs) 120; molecular wt.--approximately 1100, are mixed together at room temperature; thereto is added cobalt tallate in an amount equivalent to 0.12% cobalt metal based on emulsion solids.

Example 5 One hundred and forty-eight parts phthalic anhydride, 280 parts linseed oil fatty acids and 95 parts glycerine are heated together with agitation, with nitrogen bubbling through the mass, to a temperature of 250 C. and held at that temperaure until the acid number is 8-10. One hundred and four parts of this resin are emulsified in 122 parts water, containing 1 part saponified rosin, 1 part sodium di-(methylamyl) sulfosuccinate and 4 parts of the condensate of octyl phenol with ethylene oxide.

Example 6 One hundred and four parts of the resin from Example 5, are dissolved in 45 parts of mineral spirits (boiling point 300400 F.) and 149 parts of this solution emulsified in 122 parts water, containing 1 part sodium di- (methylamyl)sulfosuccinate, 1 part saponified rosin, and 4 parts of the condensate of 1 mol refined tall oil fatty acids with 15 mols of ethylene oxide.

Example 7 0.35 part litharge, 350 parts soya bean oil, and parts pentaerythritol are alcoholized by heating together to 250 C. and holdingfor 1 hour. Then 148 parts phthalic anhydride are added and the resinous material held at 240 C. for several hours until the acid number is approximately 8. The resin is cooled to 150 and dissolved in mineral spirits (boiling point 300-400 F.) to a 70% concentration of resin. 149 parts of this solution is emulsified in the same manner as in Example 6.

Example 8 One hundred and forty-eight parts phthalic anhydride, 160 parts soya oil fatty acids, 42 parts tung oil and parts glycerine are heated as in Example 5 to 225 C. and held until the acid number is 8-12, then cooled to 160 C., and dissolved in mineral spirits to a 50% concentration. 208 parts of this solution are emulsified in 122 parts of Water, containing 1 part sodium di-(methylamyl)sulfosuccinate, 1 part saponified rosin, and 4 parts of the condensate of 1 mol refined tall oil fatty acids with 15 mols of ethylene oxide.

Example 9 One hundred and forty-eight parts phthalic anhydride, 190 parts distilled tall oil, 30 parts tall oil fatty acids, 28 parts ethylene glycol, and 82 parts pentaerythritol are heated, as in Example 5, to 250 C. and held about 1% hours to an acid number of 16-20. This is cooled to 180 C., and cut to 50% solids in xylene. 208 parts of this solution are emulsified as in Example 8.

Example 10 Two hundred and eight parts of the resin solution of Example 6 are emulsified in 122 parts of hot water contain-ing 4 parts of oil-soluble petroleum sulfonate.

Example 11 One hundred and forty-nine parts of the resin solution, prepared as in Example 6, are emulsified in 122 parts of water containing 4 parts stearamidopropylbenzyldimethyl ammonium chloride.

Example 12 Thirty-five parts of a resin prepared as in Example 5 is emulsified by the use of a homogenizer with 65 parts of an aqueous solution containing 7.7% casein, 4.6% ammonia (28% NH OH) and 1.6% triethanolamine.

Example 13 One hundred parts of a resin prepared as in Example 5 is emulsified in parts of an aqueous solution containing 4 parts oleic acid and 4 parts morpholine.

Example 14 One hundred and forty-eight parts phthalic anhydride, 84 parts glycerine, and 84 parts linseed oil fatty acids are reacted at 220 C. to an acid number of 40-45, cooled to C. and then emulsified as in Example 12.

Example 15 One hundred and forty-eight parts phthalic anhydride, 90 parts gly-cerine, and parts castor oil are heated to 280 C. with agitation and nitrogen sparging and held 1 hour, then cooled to 230 C. and held to an acid number of 6-10; after cooling to 130 C. this alkyd is emulsified as in Example 13 above.

Example 16 One hundred and forty-eight parts phthalic anhydride, 113 parts linseed oil fatty acids, 60 parts tung oil, and 85 parts glycerine are reacted as in Example 5 at 200 C. to an acid number of 20-30. After cooling to 125 C. the alkyd is emulsified as in Example 12 above.

Example 17 One hundred and forty-eight parts phthalic anhydride, 170 parts soya oil fatty acids, 50 parts castor oil, and 92 parts glycerine are reacted as in Example 15 to an acid number of 6l0. After cooling to 125 C. the alkyd is emulsified as in Example 12.

Example 18 Samples of 100 pounds of bituminous coal in lumps of from 2 to 8 inches are sprayed with the alkyd resins of Examples 1, 2, 3, 4, 6, 8, 9, and 12 after. these resins have been diluted to 12% solids. The dry coal is sprayed at the rate of 10 pounds of resin solids per ton of coal. After standing overnight the lumps of coal can be picked up and handled with very little rub-off. The shiny surface of the coal is not impaired. When exposed to wind and rain by allowing the coal to stand out in a southern New England climate, the rate of spalling is found to be markedly reduced.

Example 19 Samples of 100 pounds of a Canadian lignite as mined are immediately sprayed with samples of the resins prepared as in Examples 1 to 17, diluted to a solids concentration at the rate of 20 pounds of resin solids per ton. The lumps of lignite are allowed to dry and found to be comparatively free from rub-off. On storage without this resin treatment moisture ordinarily is liberated from this coal causing the surface layers to loosen and spall badly. The above treatment eliminates this condition and imparts a bright shiny surface to the coal, which is dull before treatment. The rate of spalling is so reduced that the treated coal is found to be suitable for burning in furnaces and fireplaces whereas the untreated coal under similar conditions is so spalled that the remaining lumps have to be separated from the slack before use.

Example 20 Four 100-pound samples of Canadian lignitic coal mined in the province of Alberta are treated separately as follows with the alkyd resin emulsion described in Example 2:

Pretreatment Antispalling treatment None Spray with 12.5 pounds of resin solids per ton with the alkyd emulsion diluted to 5% solids with water.

2 Spray with two gal- Spray with pounls of resin Ions of water. solids per ton with the alkyd emulsion diluted to 12% solids.

3 Spray with two gal- Spray with 7.5 poumds of resin lons of water consolids per ton with the alkyd tainin 0.05% emulsion diluted to 12% solids. sodium di-(Z-ethylhexyl)sulfosuccinate.

4 None Spray with 7.5 pounds of resin solids per ton with the alkyd emulsion diluted to 12% solids the emulsion also contains 0.05 a di-(2ethylhexyl) sulfosuccinato.

Example 21 A 100-pound sample of the lignitic coal described in Example 20 is dipped in a tank containing the alkyd emulsion described in Example 2 diluted to 4% resin solids.

The coal is removed, and allowed to drain and dry for 24 hours. The coal then exhibits a firm shiny surface which may be handled without soiling the hands.

Example 22 One hundred pounds of briquetted bituminous coal is sprayed with the alkyd emulsion described in Example 2. The emulsion contains 10% resin solids used in amounts of 4.0 lb./ton of coal. The surfaces of the briquettes thus treated no longer smudge the hands when the briquettes are handled. The treatment solves a handling problem which has been troublesome to coal venders for many years.

Example 23 Fifty pounds of maple charcoal is sprayed at the rate of 10 pounds per ton of dry solids with a 4.4% solids dilution of the resin of Example 2. The charcoal is allowed to stand overnight to dry. The individual pieces of charcoal may be handled with the fingers with a minimum of rub-off, and attrition of the charcoalis markedly reduced. The burning characteristics are not deleteriously elfected. When a beef steak is grilled over a fire of the treated charcoal, the taste, flavor and characteristics appear to be the same as when grilled over a fire of untreated charcoal.

Similarly a 50-pound lot of briquetted charcoal is treated with the alkyd emulsion described in Example 2 at a concentration of 5% solids and in amounts of 5.0 pounds of resin solids per ton of charcoal. Surface rubolf was eliminated by this treatment and the handling characteristics of the briquettes definitely enhanced.

Example 24 A resin composition similar to that described in Example 2, and containing 47% resin solids, or diluted with water was sprayed on a roof of a haulageway of a coal mine. Concentrations of resin solids were varied from 10% to 47% in a series of separate tests and the resin emulsions applied at the rate of 0.44 to 2.26 pounds of resin solids per square feet of roof surface. After this spraying, the roof was given no further treatment for a period of six months, then was examined to determine the extent to which spalling had taken place, and was compared in this regard with an adjacent, untreated section of the mine roof. The conditions of the various separate tests in this series are summarized in the following table:

Pounds resin solids per 100 Percent resin solids sq. feet 12%. 47. Less than 1%. Control-no treatment. 100%.

Applied on two equal sprayings three days apart.

The above data demonstrates the effectiveness of the treatment with the resin emulsion for preventing spalling of the roof surfaces.

Example 25 A tunnel used to ventilate a coal mine was also treated with the resin emulsion described in Example 14. In this case, spalling of the untreated walls and ceiling of the tunnel was excessive during the summer months because of the high moisture content of the air supplied from the warm outside atmosphere. Condensation of moisture on the tunnel walls and ceiling acted upon the surfaces of the ceiling and walls, and caused the surface layers to loosen and fall. Such spalling was limited to less than 1% of the total surface area of the walls and ceiling by spraying with 24% to 50% resin emulsions such as are described in Examples 2, 3 and 4, in amounts of 1.4 to 6.5 pounds of resin solids per 100 square feet of surface. Adjacent roof areas, left untreated during these tests, were completely spalled over their entire surfaces.

Example 26 J In the construction of a diversion tunnel for a dam, three types of strata, a cleavable shale, a sandy shale, and a hard clay, were encountered; the first two weather badly in about 2 to 5 days after exposure. The resin emulsion of Example 2 in a concentration of 47% resin solids Was sprayed upon the exposed surfaces of the tunnel after spraying such surfaces with high pressure water to remove loose particles which interfere with resin coating. Emulsions, at the rate of 4.1 and 8.2 pounds resin solids per 100 square feet of surface, were applied in separate test areas. Essentially no weathering of treated areas was noted in a two-month period following this treatment, whereas air-slaking and spalling were immediately apparent after a three-day exposure of untreated areas.

Example 27 A test similar to that described in Example 26 was repeated on the walls of the tunnel, described in that example. A resin emulsion of 47% resin solids described in Example 2 was applied at the rate of 4.1 pounds of resin solids per 100 square feet. The treated surfaces were allowed to dry overnight, and then were coatedwith a 1-inch layer of concrete composed of 1 part Portland cement and 2 parts sand mixed with water. The concrete bonding characteristics of the resin coating surfaces were excellent and a firmly adhering concrete coating was obtained by this treatment.

The emulsion is stable in the presence of electrolytes so that if the walls of the tunnel have dissolved mineral salts or acids from the oxidation of mineral values, the emulsion forms a stabilizing film. An emulsion which is freeze-thaw stable and stable in the presence of such electrolytes is unusual.

I claim:

1. The process of protecting the surface of coal from rub-off and spalling which comprises coating the surface of discrete lumps of coal with an emulsion of an alkyd 'resin in water at the rate of from 1 to 50 pounds of resin solids per ton of coal and drying the emulsion, thus causing said emulsion to form a stable, alkyd resin-containing, protective coating on the individual coal pieces.

2. The process of claim 1 in which the surface of the coal is coated by spraying with an emulsion of the alkyd resin containing from 2% to 25% resin solids.

3. The process of claim 1 in which the coal is coated by dipping the lumps of coal in the aqueous resin emulsion containing from 1% to 15% resin solids.

4. The process of protecting the surface of lumps of lignite from rub-off and spalling which comprises coating the surface of the individual lumps of lignite with an emulsion of an alkyd resin in water at the rate of from 1 to 50 pounds of resin solids per ton of lignite and drying the emulsion, thus causing said emulsion to form a stable, alkyd resin-containing, protective coating on the individual lumps of lignite.

5. The process of protecting the surface of lumps of coal from rub-off and spalling which comprises coating the surface of lumps of coal having a size of from 2 to 8 inches with an emulsion of alkyd resin in water at the rate of from 1 to 50 pounds of resin solids per ton of coal and drying the emulsion, thus causing said emulsion to form a stable, alkyd resin-containing, protective coating on the individual lumps of coal.

6. The process of protecting solid coal surfaces from rub-off and spalling which comprises coating the surface of the coal with an emulsion of an alkyd resin in water at the rate of from about 0.25 to about 10 pounds of resin solids per square feet of exposed surface, and drying the emulsion, thus causing said emulsion to form a stable, alkyd resin-containing protective coating on the coal surface.

7. The process of claim 6 in which the surface of the coal is coated by spraying with an emulsion of the alkyd resin containing from 2 to 50% resin solids.

8. The process of protecting the surfaces of mineral formations from spalling which comprises coating the unbroken surface of the formation with an emulsion of an alkyd resin in water at the rate of from about 0.25 to about 10 pounds of resin solids per 100 square feet of exposed surface, and drying the emulsion, thus causing said emulsion to form a stable, alkyd resin-containing, protective coating on the formation surface.

9. The process of claim 8 in which the surface of the mineral formation is coated by spraying with an emulsion of the alkyd resin containing from 2-to 50% resin solids.

References Cited in the file of this patent UNITED STATES PATENTS Re. 16,914 Trent Mar. 20, 1928 2,035,520 Baird Mar. 31, 1936 2,204,781 Wattles June 18, 1940 2,222,370 Mori Nov. 19, 1940 2,272,057 Cheetham Feb. 3, 1942 2,346,650 Bernstein Apr. 18, 1944 2,413,901 Abernathy Jan. 7, 1947 2,448,605 Klenicke Sept. 7, 1948 2,822,251 Swinehart Feb. 4, 1958 2,854,347 Booth et al. Sept. 30, 1958 FOREIGN PATENTS 239,922 Great Britain Sept. 17 1925 

1. THE PROCESS OF PROTECTING THE SURFACE OF COAL FROM RUB-OFF AND SPALLING WHICH COMPRISES COATING THE SURFACE OF DISCRETE LUMPS OF COAL WITH AN EMULSION OF AN ALKYD RESIN IN WATER AT RATE OF FROM 1 TO 50 POUNDS OF RESIN SOLIDS PER TON OF COAL AND DRYING THE EMULSION, THUS CAUSING SAID EMULSION TO FORM A STABLE, ALKYD RESIN-CONTAINING, PROTECTIVE COATING ON THE INDIVIDUAL COAL PIECES. 